The objective of this Phase 1 project is to improve an effective treatment of recurrent small-cell lung cancer (rSCLC) by targeting a tumor-specific abnormal receptor, AbnV2 that is a surface-marker of the disease. Currently, there is no effective treatment for rSCLC. Our data show expression of this abnormal vasopressin V2 receptor (AbnV2 ) is a common feature of recurrent as well as primary cancers, and can be targeted by polyclonal and monoclonal antibodies recognizing unique features in a C-terminal extracellular domain. They are absent from normal tissues. Polyclonal Abs can inhibit in vitro the growth of cancer cells derived from recurrent as well as primary tumors. Expression of such receptors therefore not only raises the possibility to develop new and successful therapies for this disease, but also methods for detecting residual tumor and monitoring treatment. Such therapies should have particular relevance to recurrent disease. The hypothesis being tested is that the AbnV2 receptor will provide a sensitive and reliable target for effective treatment of recurrent rSCLC, and that monoclonal antibodies can serve as effective therapeutic targeting agents. Phase 1 goals are directed towards:(i) performing a 'proof of principle'evaluation of the effectiveness of unmodified and/or 90Y-labeled anti-AbnV2 monoAb to destroy/prevent growth of variant (and recurrent disease derived) NCI H82 and classical (and primary tumor-derived) NCI H345 SCLC cells grown in athymic mice;(ii) establishing the distribution and abundance in SCLC tumors of AbnV2 receptor protein and its unique expression by these tumors, and;(iii) determining the ability of anti-AbnV2 monoAb to inhibit the growth of SCLC cells in culture, and exploring mechanisms through which growth inhibition is accomplished. Treatment with forms of anti-AbnV2 monoAb will be compared with ubiquitous immunoglobulin (MOPC21). These investigations are designed to employ, tumor targeting in a mouse model, cytofluorographic and radiometric quantitation, antibody modification, tumor growth assessments, assessment of apoptotic and necrotic changes, IHC, ELISA, RIA, flow cytometry, RT-PCR, DNA sequencing, and Western analysis with densiometric quantitation. The approach employed is considered innovative because it represents the first treatment of form of recurrent SCLC cancer with an unmodified tumor-specific antibody. It is also provides the possibility that treatment progress can be monitored by use of radio-labeled fragments of the same antibody. A successful end-point of our Phase 1 studies would be the clear determination that unmodified, and/or 90Yttrium-labeled, anti-AbnV2 antibody can destroy or significantly curtail the growth of SCLC tumors in vivo, and that AbnV2 is a marker for >50% of SCLC tumors. Phase 2 would involve the preclinical testing of chimeric and humanized forms of anti-AbnV2 on SCLC. The proposed research is expected to rapidly lead to new and successful therapeutic approaches for managing recurrent small-cell lung cancer. rSCLC resists all current efforts at treatment. PUBLIC HEALTH RELEVANCE: This project will introduce a new targeted therapeutic approach for the treatment of recurrent small-cell lung cancer, a disease that is refractory to all current treatments. This refractoriness means <10% expected 5 year survival rate for patients representing >40,000 new cases of SCLC that arise in the USA each year. Our targeted approach is directed at a newly discovered abnormal receptor which seems to be a tumor-specific surface marker of recurrent small-cell lung cancer. Targeting will employ an available monoclonal antibody to treat this deadly disease. This antibody recognizes a unique extracellular portion of the marker. Currently patients with recurrent SCLC usually succumb to the disease in 3 to 6 months. The proposed research is expected to lead to new successful therapies for managing recurrent SCLC, thereby leading to a higher long- term survival rate for these patients.